1. Field of the Invention
The present invention relates to an electronic musical instrument and, more particularly, to a technique suitably used in an electronic musical instrument comprising an effect adder that adds acoustic effects such as a reverberation tone or the like to the input tone signal.
2. Description of the Prior Art
Conventionally, in an electronic musical instrument such as an electronic organ, addition of acoustic effects such as reverberation, and the like can give profoundness and depth to tones like in acoustic musical instruments, and such effects are important factors in colorful musical expressions. For this purpose, in most of conventional electronic musical instruments, for example, a microprocessor (CPU) controls the operation of an effect adder to add acoustic effects.
Such electronic organ or the like normally comprises an expression pedal that accentuates tones by controlling the overall volume. Furthermore, the electronic organ comprises a MIDI terminal for receiving an external MIDI signal to play, and a sequencer for performing an auto-play in accordance with a predetermined sequence pattern. The volume is controlled along with the progress of a music piece in accordance with such data.
FIG. 9 shows an example of the arrangement of a conventional electronic musical instrument comprising a reverberation device, expression pedal, and the like. As shown in FIG. 9, a reverberation device 2 comprises a DSP (digital signal processor) 1, and makes predetermined calculations of a digital tone signal input from a tone generator 10 using various coefficients, thereby adding a reverberation effect.
The tone signal added with the reverberation effect by the reverberation device 2 is mixed by an adder 3 with the tone signal to which the reverberation is not effected. The mixed signal is supplied to a D/A converter 15. The tone signal is converted into an analog signal by the converter 15. The analog tone signal is supplied to a loudspeaker 18 via a VCA (Voltage Controlled Amplifier) 19, master volume 16, and amplifier 17, thus producing actual tones.
The VCA 19 controls the overall volume (accent) on the basis of the operation of an expression pedal (to be referred to as an EXP pedal hereinafter) 7, a MIDI signal input from an external device (not shown) to a MIDI terminal 13, or a sequence pattern supplied from a sequencer 14.
For example, data of the operation amount (to be referred to as EXP data hereinafter) of the EXP pedal 7, which has been A/D-converted by an A/D converter 8, is temporarily supplied to a CPU 9. The EXP data is converted into an analog signal by a D/A converter 20, and the analog signal is supplied to the VCA 19. The VCA 19 controls the volume of an analog tone signal supplied from the D/A converter 15 in accordance with the signal corresponding to the operation amount of the EXP pedal 7 and supplied from the D/A converter 20, and outputs the controlled signal.
The MIDI signal or sequence pattern includes data corresponding to the EXP data, and such data is supplied to the D/A converter 20 as in the above-mentioned case. The EXP data converted into an analog signal is supplied to the VCA 19. The VCA 19 controls the volume of an analog tone signal supplied from the D/A converter 15 in accordance with the signal supplied from the D/A converter 20, and outputs the controlled signal to the next stage.
However, in the conventional electronic musical instrument, the reverberation tone added by the reverberation device 2 is influenced by changes in volume based on the EXP data from the EXP pedal 7, MIDI terminal 13, or sequencer 14, resulting in unnatural attenuation characteristics. This problem will be explained below with reference to FIG. 2.
(a) of FIG. 2 shows changes in operation amount data of the EXP pedal 7, i.e., the state wherein the EXP pedal 7 begins to be released from the pressed state at time A, is fully released at time B, begins to be pressed again from time C, and is fully pressed at time D. (b) of FIG. 2 shows a tone signal to which reverberation is not effected. (c) of FIG. 2 shows a tone signal added with the reverberation effect.
As shown in (b) of FIG. 2, when the EXP pedal 7 has been fully pressed, a tone signal (to be referred to as an original tone hereinafter) output from the tone generator 10 is directly output from the VCA 19 to the master volume 16, as denoted by reference numeral 21. On the other hand, when the EXP pedal 7 is fully released, the volume of the tone signal is suppressed by the VCA 19, and that signal is output, as denoted by reference numeral 22.
The volume control using the EXP pedal 7 is done for not only the original tone but also the reverberation tone. More specifically, as shown in (c) of FIG. 2, when the EXP pedal 7 has been fully pressed, the reverberation tone added to the original tone is directly output without suppressing its volume, as denoted by reference numeral 23. On the other hand, when the EXP pedal 7 is gradually released, the volume of the reverberation tone added to the original tone is suppressed according to the operation amount of the EXP pedal 7, and the suppressed tone is output.
For example, when the EXP pedal 7 is gradually released from time A to time B, the volume of the reverberation tone is suppressed during this interval, as denoted by reference numeral 24. As can be seen from (c) of FIG. 2, when the EXP pedal 7 is released while the reverberation tone is being added, the reverberation tone converges quicker than that obtained by pressing the EXP pedal 7, resulting in an unnatural tone.
When the EXP pedal 7 is pressed from time C to time D, the volume of the reverberation tone, that has been suppressed by the VCA 19 before pressing, is not suppressed after pressing. That is, after the EXP pedal 7 is pressed, the reverberation tone (the same as that denoted by reference numeral 23) added to the original tone is output without suppressing its volume, as denoted by reference numeral 25. This is no longer a reverberation tone but is a very unnatural tone that never occurs in natural environments.
As described above, in the conventional electronic musical instrument, when the operation amount of the EXP pedal is changed during addition of the reverberation effect, the reverberation tone added by the reverberation device 2 is influenced by changes in volume by the EXP pedal 7, thus outputting a very unnatural tone. The same applies to plays based on a MIDI signal or sequence pattern. That is, the reverberation tone should have a given attenuation constant that simulates the play sound field, but is unnaturally influenced by the operation of the EXP pedal.